Can infections protect against autoimmunity?

Serum IgG Profiling of Toddlers Reveals a Subgroup with Elevated Seropositive Antibodies to Viruses Correlating with Increased Vaccine and Autoantigen Responses

Purpose

The human antibody repertoire forms in response to infections, the microbiome, vaccinations, and environmental exposures. The specificity of such antibody responses was compared among a cohort of toddlers to identify differences between seropositive versus seronegative responses.

Methods

An assessment of the serum IgM and IgG antibody reactivities in 197 toddlers of 1- and 2-years of age was performed with a microfluidic array containing 110 distinct antigens. Longitudinal profiling was done from years 1 to 2. Seropositivity to RNA and DNA viruses; bacteria; live attenuated, inactive, and subunit vaccines; and autoantigens was compared. A stratification was developed based on quantitative variations in the IgG responses. Clinical presentations and previously known genetic risk alleles for various immune system conditions were investigated in relation to IgG responses.

Results

IgG reactivities stratified toddlers into low, moderate, and high responder groups. The high group (17%) had elevated IgG responses to multiple RNA and DNA viruses (e.g., respiratory syncytial virus, Epstein-Barr virus, adenovirus, Coxsackievirus) and this correlated with increased responses to live attenuated viral vaccines and certain autoantigens. This high group was more likely to be associated with gestational diabetes and an older age. Genetic analyses identified polymorphisms in the IL2RB, TNFSF4, and INS genes in two high responder individuals that were associated with their elevated cytokine levels and clinical history of eczema and asthma.

Conclusion

Serum IgG profiling of toddlers reveals correlations between the magnitude of the antibody responses towards viruses, live attenuated vaccines, and certain autoantigens. A low responder group had much weaker responses overall, including against vaccines. The serum antibody screen also identifies individuals with IgG responses to less common infections (West Nile virus, parvovirus, tuberculosis). The characterization of the antibody responses in combination with the identification of genetic risk alleles provides an opportunity to identify children with increased risk of clinical disease.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10875-021-00993-w.

Microbes and Viruses Are Bugging the Gut in Celiac Disease. Are They Friends or Foes?

The links between microorganisms/viruses and autoimmunity are complex and multidirectional. A huge number of studies demonstrated the triggering impact of microbes and viruses as the major environmental factors on the autoimmune and inflammatory diseases. However, growing evidences suggest that infectious agents can also play a protective role or even abrogate these processes. This protective crosstalk between microbes/viruses and us might represent a mutual beneficial equilibrium relationship between two cohabiting ecosystems. The protective pathways might involve post-translational modification of proteins, decreased intestinal permeability, Th1 to Th2 immune shift, induction of apoptosis, auto-aggressive cells relocation from the target organ, immunosuppressive extracellular vesicles and down regulation of auto-reactive cells by the microbial derived proteins. Our analysis demonstrates that the interaction of the microorganisms/viruses and celiac disease (CD) is always a set of multidirectional processes. A deeper inquiry into the CD interplay with Herpes viruses and Helicobacter pylori demonstrates that the role of these infections, suggested to be potential CD protectors, is not as controversial as for the other infectious agents. The outcome of these interactions might be due to a balance between these multidirectional processes.

Acute disseminated encephalomyelitis progressing to multiple sclerosis: are infectious triggers involved?

Acute disseminated encephalomyelitis (ADEM) and multiple sclerosis (MS) are demyelinating disorders affecting the central nervous system. An autoimmune aetiology has been proposed for both. ADEM principally affects adolescents following acute infection by a variety of pathogens and has also been reported to occur following vaccination. ADEM typically resolves following medical treatment, whereas MS follows a more relapsing and remitting course. The pathogenesis of MS remains unclear, but it is thought that a combination of infectious and non-infectious environmental factors and host genetics act synergistically to cause disease. A variety of viruses, including Epstein Barr virus, cytomegalovirus, herpes simplex virus and varicella zoster virus, have been implicated as possible infectious triggers. The similar clinical and pathological presentation of ADEM and MS presents a diagnostic challenge for distinguishing ADEM from a first episode of MS. Some cases of ADEM progress to MS for reasons that are not currently clear. This review examines the evidence for infectious agents as triggers for ADEM progressing to MS and suggests potential methods that may facilitate identification of infectious agents that may be responsible for the pathogenesis of ADEM to MS.

Tracing environmental markers of autoimmunity: introducing the infectome

We recently introduced the concept of the infectome as a means of studying all infectious factors which contribute to the development of autoimmune disease. It forms the infectious part of the exposome, which collates all environmental factors contributing to the development of disease and studies the sum total of burden which leads to the loss of adaptive mechanisms in the body. These studies complement genome-wide association studies, which establish the genetic predisposition to disease. The infectome is a component which spans the whole life and may begin at the earliest stages right up to the time when the first symptoms manifest, and may thus contribute to the understanding of the pathogenesis of autoimmunity at the prodromal/asymptomatic stages. We provide practical examples and research tools as to how we can investigate disease-specific infectomes, using laboratory approaches employed from projects studying the “immunome” and “microbiome”. It is envisioned that an understanding of the infectome and the environmental factors that affect it will allow for earlier patient-specific intervention by clinicians, through the possible treatment of infectious agents as well as other compounding factors, and hence slowing or preventing disease development.

Secreted proteins from the helminth Fasciola hepatica inhibit the initiation of autoreactive T cell responses and prevent diabetes in the NOD mouse

Infections with helminth parasites prevent/attenuate auto-inflammatory disease. Here we show that molecules secreted by a helminth parasite could prevent Type 1 Diabetes (T1D) in nonobese diabetic (NOD) mice. When delivered at 4 weeks of age (coincident with the initiation of autoimmunity), the excretory/secretory products of Fasciola hepatica (FhES) prevented the onset of T1D, with 84% of mice remaining normoglycaemic and insulitis-free at 30 weeks of age. Disease protection was associated with suppression of IFN-γ secretion from autoreactive T cells and a switch to the production of a regulatory isotype (from IgG2a to IgG1) of autoantibody. Following FhES injection, peritoneal macrophages converted to a regulatory M2 phenotype, characterised by increased expression levels of Ym1, Arg-1, TGFβ and PD-L1. Expression of these M2 genetic markers increased in the pancreatic lymph nodes and the pancreas of FhES-treated mice. In vitro, FhES-stimulated M2 macrophages induced the differentiation of Tregs from splenocytes isolated from naïve NOD mice. Collectively, our data shows that FhES contains immune-modulatory molecules that mediate protection from autoimmune diabetes via the induction and maintenance of a regulatory immune environment.

Isolation and structural identification of glycopolymers of Bifidobacterium bifidum BIM B-733D as putative players in pathogenesis of autoimmune thyroid diseases

Bifidobacterium bifidum 791 (commercially available as B. bifidum BIM B-733D) cell-surface biopolymers (BPs) interact selectively with human serum thyroid peroxidase (TPO) and thyroglobulin (Tg) autoantibodies (anti TPO and anti Tg, respectively). BPanti-TPO and BPanti-Tg were isolated from the soluble fraction of B. bifidum BIM B-733D by affinity chromatography with anti-TPO or anti-Tg, respectively. Homogeneity of affinity eluates (AEanti-TPO and AEanti-Tg) was tested by size exclusion chromatography. For each AE, the elution profiles generated on the basis of absorbance at 280 nm do not conform to ELISA data for functional activity characteristic of BPs. Moreover, high functional activity was detected in chromatographic fractions that had significantly different molecular weights and no absorbance at 280 nm, which suggests a non-protein (carbohydrate) nature of BPanti-TPO and BPanti-Tg. The semi-preparative size exclusion chromatography of AEanti-TPO and AEanti-Tg with detection by refractometer gave 5,000-7,000 Da fractions containing substances that interact selectively with either anti TPO (BPanti-TPO) or anti-Tg (BPanti-Tg) according to ELISA data. Analysis by two-dimensional NMR spectroscopy including a 1H, 13C-heteronuclear single-quantum coherence experiment indicated that both substances are linear α-1,6-glucans. For the first time, an immunological similarity (molecular mimicry) of glycopolymers of B. bifidum BIM B-733D and human thyroid proteins, TPO and Tg, was shown. On the whole, our data point to a possible role of bifidobacteria in the pathogenesis of autoimmune thyroid diseases (ATD). The main requirements for triggering/acceleration or prevention/abrogation of ATD by bifidobacteria through molecular mimicry mechanism are hypothesised to be (1) genetic predisposition to ATD and (2) intestinal epithelium penetration by α-1,6-glucan.

Infectome: a platform to trace infectious triggers of autoimmunity

The "exposome" is a term recently used to describe all environmental factors, both exogenous and endogenous, which we are exposed to in a lifetime. It represents an important tool in the study of autoimmunity, complementing classical immunological research tools and cutting-edge genome wide association studies (GWAS). Recently, environmental wide association studies (EWAS) investigated the effect of environment in the development of diseases. Environmental triggers are largely subdivided into infectious and non-infectious agents. In this review, we introduce the concept of the "infectome", which is the part of the exposome referring to the collection of an individual's exposures to infectious agents. The infectome directly relates to geoepidemiological, serological and molecular evidence of the co-occurrence of several infectious agents associated with autoimmune diseases that may provide hints for the triggering factors responsible for the pathogenesis of autoimmunity. We discuss the implications that the investigation of the infectome may have for the understanding of microbial/host interactions in autoimmune diseases with long, pre-clinical phases. It may also contribute to the concept of the human body as a superorganism where the microbiome is part of the whole organism, as can be seen with mitochondria which existed as microbes prior to becoming organelles in eukaryotic cells of multicellular organisms over time. A similar argument can now be made in regard to normal intestinal flora, living in symbiosis within the host. We also provide practical examples as to how we can characterise and measure the totality of a disease-specific infectome, based on the experimental approaches employed from the "immunome" and "microbiome" projects.

Infection and autoimmune disease

Most infectious agents, such as viruses, bacteria and parasites, can trigger autoimmunity via different mechanisms. The development of an autoimmune disorder after infection tends to occur in genetically susceptible individuals. Some parameters, such as genetic predisposition, feature of the infectious agent and sometimes protective effect of the infections, have a significant role in this process. These parameters and various pathogens that could lead to enhancement or exacerbation of autoimmune disease were examined in this review. Recent studies were reviewed from a microbiological perspective.

OdDHL inhibits T cell subset differentiation and delays diabetes onset in NOD mice

Some infectious diseases have been shown to halt the onset of autoimmune disease in animal models and have been suggested to also influence autoimmune pathology in humans. The isolation and study of small molecules and proteins from the infectious agents responsible for the protective effect will enable a mechanistic understanding of how these components may prevent or delay the onset of autoimmunity. In this study we confirm that the quorum-sensing signal molecule OdDHL from Pseudomonas aeruginosa can delay the onset of type 1 diabetes in the NOD mouse model. Furthermore, using an antigen-presenting cell-free system, we find not only that OdDHL inhibits the proliferation of naïve T cells but also that it directly inhibits the differentiation of T cell subsets. OdDHL was shown to have no effect on the inhibition of primed and committed differentiated T cell responses, suggesting that that immune mechanism mediated by this molecule may be more restricted to initial stages of infection.

Environmental triggers of multiple sclerosis

Multiple sclerosis is a chronic immune-mediated disease of the central nervous system that develops in young adults with a complex genetic predisposition. Similar to other autoimmune disease, HLA-DR and -DQ alleles within the HLA class II region on chromosome 6p21 are by far the strongest risk-conferring genes. Less robust susceptibility effects have been reported for non-MHC related genetic variants. Improvements in the design of epidemiological studies helped to identify consistent environmental risk-associations such as the increased susceptibility for MS in individuals with a history of infectious mononucleosis, a symptomatic primary infection with the human γ-herpesvirus Epstein-Barr virus (EBV). Sun exposure and serum vitamin D levels are emerging non-infectious environmental risk factors that may have independent roles. The analysis of environmental effects will likely expand in the next few years and will allow for the generation of testable hypotheses as to how environmental insults interact with genetic factors to jointly determine the susceptibility to MS. Insights gained from these studies might facilitate the development of prevention strategies and more effective treatments for MS.

Infection in systemic lupus erythematosus: friend or foe?

Infectious agents have long been implicated in the pathogenesis of systemic lupus erythematosus. Common viruses, such as the Epstein-Barr virus, transfusion transmitted virus, parvovirus and cytomegalovirus, have an increased prevalence in patients with systemic lupus erythematosus. They may contribute to disease pathogenesis through triggering autoimmunity via structural or functional molecular mimicry, encoding proteins that induce cross-reactive immune responses to self antigens or modulate antigen processing, activation, or apoptosis of B and T cells, macrophages or dendritic cells. Alternatively, some infectious agents, such as malaria, Toxoplasma gondii and Helicobacter pylori, may have a protective effect. Vaccinations may play dual roles by protecting against friend and foe alike.